4/8 simplified to 1/2 because out of eight there are 4 even and 4 odd numbers 0.50
We know the yint, so lets find the slope. (0,-12) and (8,-2) -2--12/8-0 or 10/8 or 1.25
So, the slope is 1.25
The answer is y=1.25x-12
11.25 - 10.5 = 0.75
Knowing that this is the profit she makes with one share, so:
20 * 0.75 = 15
Caroline made $15 profit.